The present invention relates to heat curable compositions and to a foaming method. More particularly, the present invention relates to the cure of a variety of cationically polymerizable materials, such as epoxy resins, with dialkylhydroxyarylsulfonium salts, in combination with certain organic oxidants, for example, iodoso-aromatic compounds, or organic peroxides with organic amine, or transition metal accelerators.
In my copending application Ser. No. 962,997, filed Nov. 22, 1978, now abandoned, for Curable Organic Resin Compositions and Foaming Method, a diaryliodonium salt is used in combination with a copper salt and certain reducing agents, such as ascorbic acid, Sn.sup.+2 compounds, or activated .alpha.-hydroxy compounds to effect the cure of a variety of cationically polymerizable organic compositions such as epoxy resins, phenol-formaldehyde resins, etc.
The present invention is based on the discovery that certain dialkylhydroxyarylsulfonium salts of the formula, EQU [R(R.sup.1).sub.a S].sup.+ [Y].sup.-, (1)
where R is a C.sub.(6-20) aromatic radical having from 1 to 3 nuclearly bonded hydroxy radicals, R.sup.1 can be the same or different C.sub.(1-8) alkyl radical or an alkylene radical capable of forming a cycloaliphatic or heterocyclic ring, Y is a non-nucleophilic anion, a is an integer equal to 1 or 2, and when R.sup.1 is alkyl, a is 2, and when R.sup.1 is alkylene, a is 1, also can be used to effect the cure of a variety of cationically polymerizable organic materials, when such arylsulfonium salts are used in combination with certain organic oxidants, for example, iodosoaromatic compounds, quinones, etc., and organic peroxides used in combination with organic amine or transition metal accelerators.